1. Field of the Invention
This invention relates to an air conditioner for an automobile. More particularly, this invention relates to an air conditioner for an automobile, which reduces the difference between the temperature of the air blown through a defrost duct against the inner face of a windshield and a temperature of the air blown through a foot duct against the occupant's foot rest and, at the same time, moderates change of temperature.
2. Description of Prior Art
The air conditioner for the automobile generally is provided with a heater unit and an intake unit for feeding air to the heater unit as disclosed by Japanese Utility Model Application Laid-open No. SHO 57(1982)-131309. The intake unit incorporates therein a fan driven by a motor and is provided with an internal air inlet for admitting the internal circulation current and an external air inlet for admitting the external air, which inlets are selectively switched by an intake door disposed further inside. Inside the heater unit is incorporated a heater core adapted to heat the air flowing into the heater unit with the heat derived from an engine cooling water. In the proximity of this heater core is disposed a mix door which adjusts the amount of air flowing into the heater core and the amount of air allowed to bypass the heater core. Where the air conditioner is expected further to cool the car interior, a cooler unit is incorporated on the upstream side of the heater unit.
FIG. 1 is a schematic diagram illustrating a conventional heater unit 1. A unit case 2 is provided in an upper portion thereof with an opening 3 for a defrost duct, in a lower portion thereof with an opening 4 for a foot duct, and in a lateral portion thereof with an opening 5 for a vent duct respectively. The defrost duct serves to blow air along the inner face of a windshield and keep the windshield from clouding, the foot duct to blow air toward the occupant's foot rest, and the vent duct to blow air into the car interior through a ventilator (not shown) incorporated in the instrument panel opposed to the occupant's seat. The unit case 2 of the heater unit 1 is provided at the center of the interior thereof with a heater core 6. With the heater core 6 as the center, a first mixing chamber 10 is formed above the core heater 6 in the proximity of the opening 4 for the foot duct. To the front side of the air inlet face of the heater core 6, a first mix door 7 is rotatably attached. By this first mix door 7, the ratio between the amount of the air flowing into the heater core 6 and the amount of the air bypassing the heater core 6 and flowing into the first mixing chamber 10 is adjusted. On the air discharge side of the heater core 6, a second mix door 8 for adjusting the amount of the air heated by passage through the heater core 6 fed into the second mixing chamber 11 and the amount of the air caused to bypass the heater core 6 and fed through a bypass route 12 into the second mixing chamber 11 and a third mix door 9 for adjusting the amount of the air heated by passage through the heater core 6 and then caused to flow into the first mixing chamber 10 and the amount of the same heated air caused to flow into the second mixing chamber 11 are rotatably attached.
Between the first mixing chamber 10 and the third mix door 9, a check valve adapted to permit advance into the first mixing chamber 10 of the air which has flowed through the heater core 6 and obstruct the flow of air from the first mixing chamber 10 to the third mix door 9. By this check valve 13, the flow of air from the first mixing chamber 10 to the third mix door 9 is prevented.
Between the first mixing chamber 10 and the second mixing chamber 11, a communicating door 14 is rotatably attached. This door 14 is completely opened while in a vent mode and a defrost mode and completely closed while in the other modes, i.e. a bi-level mode, a foot mode and a heater mode. The numeral symbol 15 denotes a guide wall adapted to preclude the effect of eddy from being exerted upon the check valve 13. These mix doors 7, 8 and 9 are adapted to be operated by the so-called temperature-adjusting levers disposed on the instrument panel in the car interior (not shown) to be manipulated by the car occupant.
In the conventional heater unit constructed as described above, it is desired to blow air through the defrost duct 3 against the inner face of the windshield and, at the same time, blow air through the foot duct against the occupant's foot rest as shown in FIG. 1, only a slight move of the temperature adjusting level from the full hot position for the maximum degree of space warming towrd the full cool side for the maximum degree of space cooling in the so-called heater mode has a possibility of sharply lowering the temperature of the air discharged through the defrost duct as shown in FIG. 2A to an extent of degrading the demisting function and adversely affecting the sensation of air-conditioning caused on the part of the occupant. The operating properties of the first, second and third mix doors 7, 8 and 9 exhibited under the foregoing condition vs. the position of the temperature-adjusting lever are illustrated in FIG. 2B.
An object of this invention, therefore, is to provide a novel air-conditioner for an automobile.
Another object of this invention is to provide an air conditioner for an automobile, so constructed that when a temperature-adjusting lever is operated to establish the heater mode for enabling air to be blown simultaneously through a defrost duct and a foot duct, the air blown out consequently through the defrost duct into the car interior is not suffered to experience any sharp fall of temperature.